1. Field of the Invention
The present invention relates to a partially-reduced iron producing apparatus for producing a partially-reduced iron by reducing agglomerates containing an iron oxide.
2. Description of the Related Art
For example, Patent Literature 1 listed below discloses a conventional technique of producing a partially-reduced iron by packing carbon composite pellets on a moving grate and heating and reducing the pellets, the carbon composite pellets not being added with a combustion carbon material.
However, the technique described in Patent Literature 1 has the following problems and a partially-reduced iron with a high degree of reduction cannot be obtained.
(1) After being dried, the carbon composite pellets are ignited with a gas torch and air is made to flow therethrough to combust and heat the carbon composite pellets. Accordingly, a portion of a packed bed of the carbon composite pellets on a side from which air enters keeps on combusting and reduction dose not proceed in this portion. Moreover, even if the reduction proceeds, the carbon composite pellets are reoxidized by air and thus the degree of reduction does not increase at all. Furthermore, since a high temperature state is maintained, a molten slag is excessively generated and an operation may thereby become difficult in some cases.
(2) The pellets having moved out of a carbonization area are heated by a high-temperature inert gas whose oxygen concentration is equal to 5% or less and metallization proceeds by using a remaining portion of carbonaceous material. However, the amount of remaining carbon is small and the degree of metallization is low. Moreover, until a lower portion of the packed bed reaches a high temperature, an upper portion of the packed bed is exposed to strong oxidizing gases such as carbon dioxide and water vapor generated from the high-temperature carbonaceous material and reoxidation of the upper portion thereby proceeds.
(3) A high-temperature gas in a metallization area where a large amount of heat is required is produced by combusting part of a flammable volatile component in the coal which is generated in the carbonization area and a CO gas which is generated by the reduction reaction. However, since the amount of flammable component is small with respect to the amount of the entire exhaust gas, a supplemental fuel is additionally required.
In view of the problems described above, for example, Patent Literatures 2 and 3 listed below each disclose a conventional technique of producing partially-reduced iron in which pellets formed by mixing and pelletizing a reduction carbon material, a fine iron ore, and a slag-forming flux are added with a combustion carbon material by coating the pellets with the combustion carbon material, the combustion carbon material is ignited, and then the pellets are subject to sintering with air being suctioned downward.